Oil well performance



June 4, 1968' w. a. LUMPKIN OIL WELL PERFORMANCE Filed Oct. 5. 1966 JJwZOFUMWZ.

ZOFUDQOWE INVENTOR W. B. LUMPKIN BY 3 i ATTORNEYS United States Patent3,386,507 OIL WELL PERFORMANCE William B. Lumpkin, Caracas, Venezuela,assignor to Phillips Petroleum Company, a corporation of Delaware FiledOct. 3, 1966, Ser. No. 583,625 5 Claims. (Cl. 16611) This inventionrelates to a process for opening up a stratum around an oil-producingwell to improve production thru the well.

Recovery of oil from producing formations is accompanied by numerousoperating problems, particularly around the production Wells into whichthe oil is driven. Flow of oil into the production well is frequentlyimpeded near the production well by emulsion blocks, solidto-semisolidasphaltic and paraffinic materials deposited from the oil passing thruthe stratum into the production well, etc. Achievement of an approach tototal recovery of available oil is difficult because of varyingreservoir conditions and methods of production resulting in bypass ofareas, partial sweep recovery, etc. In fact, in certain fields whichproduce heavy grades of crude oil, the recovery by primary methodsamounts to only about 5 percent of the in-place oil.

One approach to the problem of improving oil production thru aproduction well comprises applying heat at high temperature to thestratum immediately surrounding the production well to increasepermeability and porosity of the surroundin annulus. Whether achieved byin situ combustion, downhole heaters, or other means, this methodincreases permeability and porosity around the wellbore, reduces oreliminates asphaltic and paraflinic deposits and emulsion or waterblocks, and, where the formation is amenable to fracturing, fracturesare-produced to increase flow of oil. However, direct application ofheat to the stratum surrounding the production well tends to move theoil away from the well.

This invention is concerned with a method or process for opening up astratum around a production well to improve production while avoidingthe driving of oil away from the production well.

Accordingly, it is an object of the invention to provide a process forimproving the flow rate of oil thru a stratum into a production well.Another object is to increase the permeability of an oil stratum in anannulus immediately surrounding a production well to increase the flowof oil into the well when production is resumed. A further object of theinvention is to open up a stratum immediately surrounding a productionwell while avoiding the driving of oil away from the well. Other objectsof the invention will become apparent to one skilled in the art uponconsideration of the accompanying disclosure.

A broad aspect of the invention, as applied to an oil stratum penetratedby an injection well and a production well, comprises opening up thestratum to the flow of gas from the injection well to the productionwell as by injecting air intothhe production well until it is producedthru the production well; thereafter igniting combustible material inthe stratum adjacent the production well to establish a combustion zone;feeding air to the combustion zone by injecting same thru the injectionwell to cause the combustion zone to move into the stratum from theproduction well in a reverse-burning operation, depositing coke in thestratum traversed by said zone; after the combustion zone has been movedinto the stratum a substantial distance, such as at least 2 feet but notmore than about of the distance between wells, substantially reducingthe air flow rate to the combustion zone so as to terminate reversemovement thereof; and, after advance of the combustion zone has beenterminated by insufficient air supply, again injecting air at asufiicient rate into the injection well to cause the combustion zone tomove back toward the production well and burn the coke deposited duringthe reverse-burning phase of the process. The reverse movement of acombustion zone in a carbonaceous stratum requires an air flow rate ofat least 20 standard cubic feet per hour of air per square foot(s.c.f./hr./ft. of cross section of stratum. Reducing the flow rate ofair substantially below this value terminates the advance of thecombustion zone toward the injection well and again increasing the flowof air has the effect of driving the combustion zone back to theproduction well. During the reverse movement of the combustion zone,coke is laid down in the stratum thru which the combustion zone passesand during the direct drive of the combustion zone back to theproduction well, this coke is consumed so as to substantially completelyburn out all of the carbonaceous material in the stratum thru which thedirect drive combustion zone passes. This cleans out the rock or sand socompletely that it is found to be white and free of carbonaceousmaterial.

In order to reverse the reverse-burning combustion zone, the flow of aircan either be substantially reduced to below 20 s.c.f./hr./ft. or it canbe terminated for a substantial period of time, such as several hours toseveral days, so that upon resumption of the injection of air at asubstantial rate, the combustion zone is driven back to the productionwell. Merely reducing the air flux to less than 20 s.c.f./hr./ft. causesreversal of the combustion zone to a direct drive back to the productionwell.

Following the opening up of the stratum around the production well bythe reverse-burning and direct-drive combustion zone technique,production of oil from the stratum into the production well is resumedwith any suitable production technique, including water drive, steamdrive, or any miscible fluid drive operable in the particular oilstratum involved.

The combustion zone in the stratum adjacent the pro duction well isestablished by any suitable method. One method comprises burning acharcoal pack in the production well to heat the adjacent formation to acombustion-supporting temperature and feeding air into the hot formationfrom the injection well. In this technique, about 24 weight percent ofnatural gas or other suitable fuel gas may be injected in the air tofacilitate the establishment of the combustion zone.

A preferred method of establishing the combustion zone comprisesinjecting an autoignitable fuel into an annulus of the stratum adjacentthe production well after establishing air permeability and causing theignition of the autoignitable fuel by injecting air thru the injectionwell and forcing same into the annulus impregnated with theautoignitable fuel. The copending application of F. A. Klein and M. R.Dean, Ser. No. 559,804, filed June 23, 1966, discloses such a method ofigniting a stratum around a well and autoignitable fuel compositionsused in such a process. Autoignitable liquid fuels include lung oil,linseed oil, tall oil, red oil, castor oil, oleic acid, linseed oilfatty acids, tall oil fatty acids, and turpentine. The autoignitablefuel may be mixed with a liquid hydrocarbon ranging from gasoline tocrude oil and may contain a minor concentration of an oil-solubleoxidation catalyst such as cobalt naphthenate to enhance the oxidationof the fuel mixture.

A more complete understanding of the invention may be had by referenceto the accompanying schematic drawing which is an elevation thru an oilstratum penetrated by injection and production wells.

Referring to the drawing, an oil stratum 10 is penetrated by aproduction well 12 and an injection well 14. Production well 12 isprovided with a tubing string 16 and injection well 14 is provided witha tubing String 18. At the stage of the process illustrated, a firefront or combustion zone has been advanced from production well 12outwardly from the well into the stratum the desired distance and thisis followed by the direct drive of the combustion zone 20 back to theproduction well. It is to be understood that injection well 14 is eitherone of a ring of injection wells around well 12 or one well in a line ofwells parallel with a line of production wells 12, there being anotherline of injection wells (not shown) on the opposite side of the line ofproduction wells 12.

Assuming that oil has been produced by fluid drive from injection well14- to production well 12 until the rate of flow of oil into well 12 hassubstantially decreased due to accumulation of plugging material in theannulus immediately surrounding well 12, the production process isterminated and air is injected thru tubing string 18 into injection well14 until air is being produced thru well 12. At this time, ignition ofthe carbonaceous material in the annulus surrounding Well 12 is effectedby any suitable means, such as those previously described. It ispreferred to inject an autoignitable liquid fuel composition into theannulus immediately surrounding well 12 and resume air injection thruwell 14 so that the flow of air into the annulus impregnated with theautoignitable fuel causes ignition thereof and, also, ignition of thein-place oil. Continued injection of air thru well 14 then advances theresulting combustion zone toward well 14 and away from well 12, asillustrated at 20. During the reverse movement of combustion zone 20away from well 12, coke is laid down in the stratum thru which thecombustion zone passes. After the combustion zone has been advanced tothe desired location away from well 12, air injection is reduced orterminated for a substantial period and then resumed so as tore-establish combustion and drive the combustion zone back to theproduction well, cleaning out the sand or rock in the annulus thru whichthe combustion zone has moved and opening up the stratum to more rapidproduction of oil. Thereafter, the fluid drive process from injectionwell 14 to production well 12 is resumed.

In the event the cleaned-out annulus later becomes impregnated withsolid-to-semisolid carbonaceous material, the same is cleaned out byagain causing a combustion zone to move out from well 12 into thestratum and back again in the manner described herein.

Certain modifications of the invention will become apparent to thoseskilled in the art and the illustrative details disclosed are not to beconstrued as imposing unnecessary limitations on the invention.

1 claim:

1. In a process for producing oil by fluid drive thru an oil stratumpenetrated by an injection well and a pro- 4 duction well wherein adriving fluid is injected into said stratum to drive oil into saidproduction well and flow into said production well is impeded bycombustible material occupying the pores of said stratum, the method ofimproving flow of said oil which comprises to steps of:

(a) injecting air into said injection well until air is being producedthru said production well;

(b) initiating combustion of carbonaceous material in said stratumadjacent said production well to establish a combustion zone;

(c) injecting air as in step (a) to feed the combustion zone of step(b), cause same to move away from said production well, and leave a cokedeposit in the area traversed by said combustion zone;

(d) continuing step (c) until said zone has moved away from saidproduction well a distance of at least 2 feet but not more than about ofthe distance between said wells;

(e) following step (d), substantially reducing the air flow rate to saidcombustion zone for a period to terminate movement of said zone awayfrom said production well;

(f) thereafter, again injecting air at a sufiicient rate to drive saidcombustion zone back to said production well and burn out the cokedeposit of step (c); and

(g) resuming the production of oil by fluid drive from said injectionwell to said production well.

2. The process of claim 1 wherein said fluid drive is a steam drive.

3. The process of claim 1 wherein said fluid drive is a water drive.

4. The process of claim 1 wherein said fluid drive is a miscible fluiddrive.

5. The process of claim 1 wherein the combustion zone in step (b) isestablished by injecting an autoignitable fuel into an annulus of saidstratum adjacent said production well and resuming air injection thrusaid injection well to contact said fuel with said air and causeignition.

References Cited UNITED STATES PATENTS 2,994,374 8/1961 Crawford et al16611 2,994,376 8/1961 Crawford et a1 16611 3,032,103 5/1962 Parker1661l 3,057,403 10/1962 Wyllie 166-2 3,062,282 11/ 1962 Schleicher166-11 3,064,728 11/1962 Gould 1662 3,126,955 3/1964 Trantham et al1661l 3,165,154 1/1965 Santourian 166-l1 3,172,467 3/1965 Trantham et a11661l X STEPHEN I. NOVOSAD, Primary Examiner.

1. IN A PROCESS FOR PRODUCING OIL BY FLUID DRIVE THRU AN OIL STRATUMPENETRATED BY AN INJECTION WELL AND A PRODUCTION WELL WHEREIN A DRIVINGFLUID IS INJECTED INTO SAID STRATUM TO DRIVE OIL INTO SAID PRODUCTIONWELL AND FLOW INTO SAID PRODUCTION WELL IS IMPEDED BY COMBUSTIBLEMATERIAL OCCUPYING THE PORES OF SAID STRATUM, THE METHOD OF IMPROVINGFLOW OF SAID OIL WHICH COMPRISES TO STEPS OF (A) INJECTING AIR INTO SAIDINJECTION WELL UNTIL AIR IS BEING PRODUCED THRU SAID PRODUCTION WELL;(B) INITIATING COMBUSTION OF CARBONACEOUS MATERIAL IN SAID STRATUMADJACENT SAID PRODUCTION WELL TO ESTABLISH A COMBUSTION ZONE; (C)INJECTING AIR AS IN STEP (A) TO FEED THE COMBUSTION ZONE OF STEP (B),CAUSE SAME TO MOVE AWAY FROM SAID PRODUCTION WELL, AND LEAVE A COKEDEPOSIT IN THE AREA TRAVERSED BY SAID COMBUSTION ZONE; (D) CONTINUINGSTEP (C) UNTIL SAID ZONE HAS MOVED AWAY FROM SAID PRODUCTION WELL ADISTANCE OF AT LEAST 2 FEET BUT NOT MORE THAN ABOUT 1/10 OF THE DISTANCEBETWEEN SAID WELLS; (E) FOLLOWING STEP (D), SUBSTANTIALLY REDUCING THEAIR FLOW RATE TO SAID COMBUSTION ZONE FOR A PERIOD TO TERMINATE MOVEMENTOF SAID ZONE AWAY FROM SAID PRODUCTION WELL; (F) THEREAFTER, AGAININJECTING AIR AT A SUFFICIENT RATE TO DRIVE SAID COMBUSTION ZONE BACK TOSAID PRODUCTION WELL AND BURN OUT THE COKE DEPOSIT OF STEP (C); AND (G)RESUMING THE PRODUCTION OF OIL BY FLUID DRIVE FROM SAID INJECTION WELLTO SAID PRODUCTION WELL.